This invention deals with a novel method of detecting leaks in a multi-layered roof.
The method is a non-electrical leak detection method which is inexpensive, accurate and less time consuming than methods currently in use today.
This method is especially advantageous on industrial and commercial buildings which typically have flat or near flat roof surfaces. The roofs that are capable of being susceptible for use of the inventive method are multi-layered, that is, they generally have in combination roof supporting structure which is surmounted by a deck, thermal insulation and ballast layers to assist in holding the roof in place.
These types of roofs tend to be economical and function quite well as long as there is no break in the water-impermeable membrane. Once the water-impermeable membrane is broken, water enters the roof deck and seeps and permeates the roof deck and eventually enters the interior of the building.
The detection of leaks in roofs is costly and time consuming because the point of entry of the water from the leaks into a structure most often is not aligned with the leak in the roofing membrane. Generally, this is so because of the numerous layers of semi-permeable components of a multi-layered roofing system. For example, a typical multi-layered roof system consists of a deck structure such as concrete, metal or wood; vapor barriers; insulation either in single or multiple layers; roofing membranes and the protective layers of gravel or stone, or the like. The problem is enhanced when a roof has been refurbished and multiple layers have been placed over multiple layers of an existing roofing system.
Leak detection is particularly difficult on large and flat or low sloped roofs because of the ready transmissions of water between the layers and because of the problem indicated supra, of multiple layers.
Small openings in the water-impermeable membrane can allow large amounts of water to enter, yet, these small openings are generally not detectable to the naked eye.
Several systems are currently in use for detecting leaks in roofs, for example, Gustafson, in U.S. Pat. No. 3,824,460. issued July 16, 1974. discloses a leakage sensor strip which is a pair of encased wires held essentially parallel to each other by a plurality of spaced webs which are an extension of the casing of the wires. The sensor strip is placed and held flat on a floor or roof deck over a certain length so that leakage anywhere along the probe will result in a capacitance change which can be sensed. Anderson, in U.S. Pat. No. 3,967,197, issued June 29, 1976, discloses a method of detecting moisture in a multi-layered roof system. The method disclosed consists of reading the capacitance at various predetermined points on a roof surface to create a base line reading and then periodically re-reading the capacitance at these same points to determine a deviation from the original reading. A capacitance meter is moved over the surface of the roof. Wherever the moisture in the roof has increased, the dielectric constant increases and the expectation is that this is indicative of a water leak.
Another system has been disclosed by Sheahan in U.S. Pat. No. 4,110,945, issued Sept. 5, 1978. In that method, a plurality of water detectors are positioned under the water-impermeable membrane of a roof. In the event that the water-impermeable membrane is broken and the roof leaks, the general area of the leak can be determined. Each such water detector is electrically powered and connected to a sensor at a location remote from the roof.
An additional disclosure of leak detection can be found in U.S. Pat. No. 4,166,244, issued Aug. 28, 1979 to Wood et al. The patent discloses a leakage detection system for radioactive waste storage tanks. The system is based on the detection of leaks of electrically conductive fluids from large tanks.
Finally, a most recent patent, U.S. Pat. No. 4,598,273, issued July 1, 1986, discloses a leak detection system for roofs which is based on a moisture intrusion detection wherein a plurality of independent and insular moisture detecting units are place in a predetermined spaced-apart relationship across the surface of a roof structure beneath a water-impermeable membrane. Each of the units includes a moisture detecting and power supply unit and signaling unit. When moisture penetrates the water-impermeable membrane of the roof structure, a leak condition exists and a water-activated battery is activated.
Mention should also be made of a copending application, U.S. Ser. No. 838,201, filed on Mar. 7, 1986, in the name of James P. Sheahan, the inventor herein, entitled "Hold Down Device" wherein the detection of leaks in multi-layered roof structures is discussed and includes the use of a device which measures conductance or the lack thereof, while also functioning as a hold down device. The device penetrates the water-impermeable membrane of the roof system and when water enters the system below the water-impermeable membrane, the hold down device senses the presence of the water.
None of the above-identified systems, however, operate as the instant invention does. None are as economical and as efficient as the method of the instant invention.